There are various kinds of IC packages that package a semiconductor device. For example, one type called LGA (Land Grid Array) in which a flattened pad is arranged, one type called BGA (Ball Grid Array) in which a spherical pad is arranged, and one type called PGA (Pin Grid Array) in which a lead pin is arranged. When the various kinds of IC packages are electrically connected with a wiring pattern on a circuit board, an IC socket which has a contact which makes electrical contact to a wiring pattern on a circuit board (for example, see Patent Documents: Japanese Patent Application Publication No. Hei 7-282931, Japanese Patent Application Publication No. Hei 10-302925, and Japanese Patent Application Publication No. 2005-19284) has been used. It is desirable to increase the density of electrical contacts of pads or the like in IC packages and the corresponding electrical contacts of IC sockets.
Prior Art FIGS. 1A-1C show a part of an existing IC socket which accepts an IC package type called LGA.
Prior Art FIGS. 1A-1C show an insulating housing 91 and a contact 92 both of which are included in an IC socket 9, an IC package 8 which is mounted in the IC socket 9, and a pad 81 of the IC package 8. In the insulating housing 91 is a recess 911 in which the IC package 8 is accepted from an upper side. A cantilever spring is applied to the contact 92, and a side of a contact point 921 shown left in Prior Art FIGS. 1A-1C is a free end. In the socket 9 which employs the contact 92 in a cantilever spring form, when the IC package 8 is pressed down (a vertical load is applied), the IC package 8 goes down with the contact 92 being bent, and a contact position slides horizontally in a plan view.
Prior Art FIG. 1A shows a state in which the IC package 8 is set from above in the recess 911 so that the IC package 8 is settled at a side in a direction in which the IC package 8 is going to slide (left side, see an arrow in Prior Art FIG. 1C). Prior Art FIG. 1B shows a state where the IC package 8 is set in the recess from above so that the IC package 8 is settled at a side opposite to the direction in which the IC package is going to slide (right side).
In the states shown in Prior Art FIGS. 1A and 1B, the contact 92 of the IC socket 9 contacts with the pad 81 of the IC package 8 set in the recess 911 of the IC socket 9. The IC package 8 set in the recess 911 of the IC socket 9 receives a vertical load by a pressing cover (not shown). Accordingly, the IC package 8 is pressed in until a bottom face 80 of the IC package abuts on a support section 912 of the insulating housing 91.
Prior Art FIG. 1C shows a state in which the IC package 8 shown in Prior Art FIG. 1B is pressed in until the bottom face 80 abuts on the support section 912 of the insulating housing 91.
When a vertical load is applied to the IC package 8 which is set at the side opposite to the direction in which the IC package is going to slide (see the arrow in Prior Art FIG. 1C), the contact 92 in a cantilever spring form of the IC socket 9 falls downward (see the contact shown by dotted line in the drawing), and the contact point 921 moves left in the drawing. At this point, an amount of the movement is described as R in the drawing. When the contact point 921 of the contact 92 is moved left in the drawing, the pad 81 of the IC package 8 slides as well by friction. Accordingly, by this friction of the sliding, the IC package also slides left in the drawing (see the arrow in Prior Art FIG. 1C). As a result, the IC package 8 abuts on the edge 911a of the recess 911, and the bottom face 80 abuts on the support section 912 of the insulating housing 91. Thus, the IC package 8 is positioned in a final predetermined mount position. In the IC socket 9 shown in Prior Art FIG. 1B, when a vertical load is applied to the IC package 8, the IC package 8 is moved left. At this point, an amount of movement is described as S in the drawing. Therefore, an amount of relative movement of the contact 921 to the pad 81 of the IC package becomes |R-S|.
In addition, by the sliding of the contact 92 and the pad 81, oxide film formed on the pad and contact is removed.
As shown in Prior Art FIG. 1A, when a vertical load is applied through the pressing cover (not shown) to the IC package set in the recess 911 in the state in which the IC package is settled at the side in the direction in which the IC package 8 is going to slide (see the arrow in of Prior Art FIG. 1C), the IC package 8 goes downward. However, because the IC package 8 is already in contact with the edge 911a of the recess 911 before the vertical load is applied, the IC package 8 may not slide left further more in the drawing. Therefore, in this case an amount of relative movement of the contact point 921 to the pad 81 of the IC package 8 is R, which is larger than the amount of relative movement of the IC socket 9 shown in Prior Art FIG. 1B whose amount of relative movement is |R-S|. Or, a contacting point of the contact 92 with the pad 91 is shifted left by R while the state is changed from where the IC package is set in the recess to where the IC package is positioned in the final predetermined mount position. Regarding the IC package 8 shown in Prior Art FIG. 1C, in consideration of the sliding distance by R in which the contacting point of the contact 92 with the pad 81 is shifted left when the IC package is set in the recess 911 in the state in which the IC package 8 is settled at the side in the direction (see the arrow in Prior Art FIG. 1C) in which the IC package 8 is going to slide as shown in Prior Art FIG. 1A, the pad 81 is made larger than an enough size required to make electrical contact with the contact point 921 of the contact 92. Therefore, density increase of an electrical contact (or pad) in an IC package is restrained. In addition, because the contact 92 of the IC socket 9 corresponds to the pad of the IC package 8, a pitch between each adjacent contact 81 becomes bigger as the pad 81 gets larger. Accordingly, density increase of an electrical contact in an IC socket is also restrained.
Referring to FIG. 1B again, the IC package 8 shown in slides to the final mount position. If a distal end 801 in a direction in which the IC package 8 slides abuts on the edge 911a of the recess 911 before the bottom face 80 of the IC package 8 abuts on the support section 912 of the insulating housing 91, friction increases because both the distal end 801 of the IC package 8 and the edge 911a of the insulating housing 91 are made of resin. Accordingly, the IC package 8 does not move further down, which is problematic. Even if the IC package 8 moves down, when the IC package 8 moves down, the bottom face 80 abuts on the support section 912 while the IC package 8 and the insulating housing 91 scrape each other.